Riser control devices have cutting rams mounted perpendicular to a workover string. The rams can be activated to sever the workover string and seal the wellbore. The cutting rams move through a horizontal plane and are often driven by in-line pistons. The arrangement of the pistons and the cutting rams make the riser control device both cumbersome and ungainly. Their physical size makes them impractical for installing within an 18.5″ bore.
Alternative methods of sealing the wellbore, such as ball valves are often used, however, these valves can be expensive to maintain and can be complicated to operate.